This application is related to Japanese Patent Application No. 2000-70479 filed on Mar. 14, 2000, whose priority is claimed under 35 USC xc2xa7119, the disclosure of which is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a particle measurement apparatus and method and more particularly to an apparatus and method for calculating a characteristic parameter by processing a signal representative of particle characteristics through a nonlinear amplifier.
2. Description of the Related Art
Particle measurement apparatuses usually employ a linear amplifier for amplifying an electrical signal obtained from particles, i.e., a particle signal to be measured.
The linear amplifier used in such apparatuses is required to maintain the precision of linearity for accurate measurements. Therefore some techniques to compensate or correct the amplification characteristics of the linear amplifier are conventionally proposed (see, Japanese unexamined patent publication Nos. Hei 7(1995)-147518 and Hei 2(1990)-206905). a non-linear amplifier, e.g., a logarithmic amplifier rather than the linear amplifier. It is because the industrial particles have a wide range of diameter from submicrons to hundreds of microns and the non-liner amplifier can conveniently cover the wide range.
However, few techniques for compensating the amplification characteristics of the non-linear amplifier have been known.
In view of such circumstances, it is an object of the present invention to provide a particle measurement apparatus and method in which the characteristics of the non-linear amplifier used for processing the particle signal are compensated so as to permit a wide range particle measurement with high precision.
The object of the present invention is attained by providing a particle measurement apparatus comprising: a particle signal detecting section for detecting a particle signal with respect to a plurality of particles, the particle signal representing characteristics of each particle; a false signal generating section for generating a false signal corresponding to the particle signal; a selecting section for selecting the particle signal or the false signal, a non-linear amplifier; a first calculating section for receiving the signal selected by the selecting section through the non-linear amplifier to calculate a characteristic parameter; a second calculating section for receiving the signal selected by the selection section not through the non-linear amplifier to calculate the characteristic parameter; a comparison section for comparing the characteristic parameters calculated by the first and second calculating sections respectively when the selecting section selects the false signal; a storage section for storing a comparison result of the comparison section; and a compensating section for compensating the characteristic parameter calculated by the first calculating section on the basis of the comparison result when the selection section selects the particle signal.
In other words, the apparatus of the present invention is so constituted as to check an input-output characteristics of the non-linear amplifier using a false signal beforehand so that when a real particle signal is amplified by the non-linear amplifier to calculate the characteristic parameter of the particle, a result of the calculation may be compensated using the aforesaid input-output characteristics.